Stencil sheet



Patented June 16, 1931 UNITED STATES PATENT orrlcr CHARLES E. KUMLI, OFCIHCAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

I SELEUIOGRAPH COMPANY, OF CHICAGO,

ILLINOIS, A CORPORATION OF ILLINOIS STENCIL SHEET No Drawing.

i yoshino paper, having a hardened coatingof '5 organiccolloid,-impervious to ink, in wh1ch the stencil characters are cut, bythe expression process, to permit the ink or other c01- oring to printthrough the fibers of the paper or other porous support.

One of the common types of stencils long in use consisted of Japaneseyoshino paper coated with gelatin which was coagulated either by a'chrome salt such as potassium dichromate, or by an aluminum salt, whichchemically combined with the gelatin to form a hard coating.

In order to adapt the coated sheet for making the stencil bypressure,asfor instance by the impact of the types of a typewriter,

the sheet must be dampened so as to permit the type to rupture theimpervious film without cutting or otherwise injuring the fiber of thepaper, or other porous support. In dam ening coated sheets which havebeen bar ened by "aluminum salts alone, the fibers of the paper have atendency to stretch so as to cause. the stencil to become baggy in theframe, and the paper has a tendency to become sticky. For this reason,aluminum salts have not 1 been satisfactory as hardening agents.

Potassium dichromate as a, hardening a ent is also objectionable becauseit necessltates two steps in the coating process.

When potassium dichromateis employed,

the stencil sheet must first be' coated with the glue or gelatin andthen coated with the hardening solution.

If the potassium dichromate were mixed with the glue or gelatin, beforebeing applied to the sheet, coagulation would'take place in thesolution, thereby rendering it diflicult to apply.

The mam objects of this invention are to I provide an improved coatingmaterial which is waterproof and which has none of the aforementionedobjectionable characteristics inherent in solutions contai ing chrome oraluminum salts; to provide coating solution which may be applied in oneopera- Application filed December 20, 1928. Seria1 No. 327,482.

tion; to provide an improved stencil sheet which is tough and waterproofand which will not become baggy when dam ened; and to provide animproved method 0 preparing stencil sheets which are to be moistenedbefore being used.

Stencils may be made of any suitable fibrous, porous material, butJapanese yoshino paper is preferred because of its thin texture.

The improved coating material comprises an organic colloid, a volatilevehicle, a tempering agent, and an ammoniacal solution of cupric hydratecommonly known as Schweitzers reagent.

The colloid is the base or binding agent. It

Nbinds together the fibers of the paper and ives strength to the sheet.A good grade of ide glue has been found to be satisfactory,

but it may be replaced by any coagulable organic colloid.

The volatile vehicle may be water or any other suitable solvent whichevaporates quickly after the film has been applied to the? sheet. 0

Glycerine is preferred as the tempering agent, but it may be replaced bysugar, glucose or any of the other well known tempering agents.

The Schweitzers reagent is the waterproofing agent. It coagulates theglueor other organic colloid to render the colloid waterproof.

In preparing this improved coating ma terial, the ingredients are mixedpreferably in two separate vessels.

In one vessel, he glue is soaked in water for a period ranging from 6 to10 hours. The glycerine is then added and the mixture heated to about 70C. These ingredients may be combined in various proportions but highlysatisfactory results can be obtained as follows:

In another vessel, copper'sulphate is dis solved in water by theapplication of heat.

The solution is then cooled and ammonium hydroxide is added.

When the first few drops of ammonium hydroxide come in contact with thesolution of copper sulphate and water, a blue pre-' cipitate of cuprichydroxide is formed. A suflicient quantity of ammonium hydroxide is usedto redissolve the cupric hydroxide.

The ingredients of the solution may be combined satisfactorily in thefollowing proortions:

Parts by weight Ounces Copper sulphate 15 ater 42 Ammonium hydroxidesolution) 9 The solutions in the two vessels are then mixed and thetemperature brought to about 40 C. At this temperature the improved ingfrom the spirit'of the invention as defined by the following claims Iclaim: 1. A coating material for stencil sheets ,comprising a mixture ofan organic colloid, 40 a tempering agent, and Schweitzers reagent.

2. A coating material for stencil sheets comprising glue, a temperingagent, and Schweitzers reagent. I

3. A coating material for stencil sheets comprising a mixture of anorganic colloid,

salt, and ammonium hydroxide.

and ammonium hydroxide.

9. A composition for use in coatingthe porous base of a stencil sheetcomprising an organic colloid about 11 parts, water about 43 parts, atempering agent about 20 ounces, copper sulphate, and ammoniumhydroxide.

10. The method of preparing a coating solution for stencils whichconsists in mixing an organic colloid and water, adding a temperingagent, and then adding Schweitzers reagent.

11. The method of preparing a coating material for stencils whichconsists in mixing an organic colloid with water and a temper ing agent,and then adding to the mixture a solution of a water soluble copper saltand ammonium hydroxide.

12. The method of preparing a coating material for stencils whichconsists in mixing an organic colloid with water and a tempering agent,and then adding to the" mixture a solution of copper sulphate, water,and ammonium hydroxide.

13. The method of reparing a coating ma-' terial for stencils w ichconsists in mlxing glue about 11 parts with water about 43 parts,addingv20 ounces of glycerine, heating the mixture, making a solution ofcopper sulphate about 15 parts, water about 42 parts,

and ammonium hydroxide about 9 parts, and then adding said solution tosaid mixture.

14. A stencil'sheet coated with.- a mixture of a protein, colloid, atempering agent, and Schweitzers r ent.

15. A stencil sheet coated with a. mixture of glue, a tempering agent,and Schweitzers reagent.

Signed at Chicago this 17th day of December, 1928.

CHARLES F. KUMLI.

a tempering agent, a water soluble copper 4. A coating material forstencil sheets comprising a mixture of glue, water, atemperlng agent, awater soluble copper salt,

and ammonium hydroxide.

: 5. A stencil sheet coated with a mixture of an'organic colloid, atempering agent, and Schweitzers rea ent.

6. A stencil s eet coated with a mixture of an organic colloid, atempering agent, a

water soluble copper salt, andammonium hydroxide.

7 A composition for use in coating the porous base of a stencil sheetcomprising a mixture of an organic colloid, a tempering agent, coppersulphate, water, and ammo-.

nium hydroxide.

8. A stencil sheet coated ,with a mixture 5 of glue, a tempering agent,copper sulphate,

